[leetcode] 961. N-Repeated Element in Size 2N Array : https://leetcode.com/problems/n-repeated-element-in-size-2n-array/

N-Repeated Element in Size 2N Array.cc

class Solution {
public:
    int repeatedNTimes(vector<int>& A) {
        set<int> s;
        for(int i=0;i<A.size();i++){
            if(s.find(A[i])!=s.end()) return A[i];
            s.insert(A[i]);
        }
        return -1;
    }
};